🚀 go-pugleaf

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1221 PM CDT MON MAY 6 2013

.DISCUSSION...
335 AM CDT

MILD TEMPS AWAY FROM THE LAKE AND LOW CHANCE POPS FOR SHOWERS ACROSS
FAR SOUTH/SOUTHEAST CWA ARE THE MAIN FORECAST CONCERNS THROUGH
MID-WEEK. FOCUS THEN TURNS TO PRECIP POTENTIAL AND COOLER
TEMPERATURES WITH FIRST COLD FRONT THURSDAY...AND SECOND STRONGER
COLD FRONT WHICH IS EXPECTED TO ARRIVE SATURDAY.

PESKY OLD UPPER LOW CONTINUES TO SPIN IN A NEARLY STATIONARY
POSITION OVER THE SOUTHEASTERN CONUS EARLY THIS MORNING...WITH
REGION OF INFLUENCE ALONG ITS NORTH/NORTHWEST PERIPHERY STILL
WRAPPING CYCLONICALLY BACK INTO PARTS OF NORTHERN IL AND INDIANA.
WHILE A FEW ISOLATED LIGHT SPRINKLES HAVE MADE IT AS FAR NORTH AS
OHARE EARLY THIS AM...CONSENSUS AMONG VARIOUS GUIDANCE APPEARS TO
INDICATE WEAK HEIGHT RISES AND DECREASING MID LEVEL VORTICITY
ADVECTION ACROSS THE FORECAST AREA TODAY...WITH LINGERING WEAK
FORCING AND MORE PLENTIFUL MID LEVEL MOISTURE TO REMAIN ONLY ACROSS
CENTRAL IL/IN AND OUR FAR SOUTHERN COUNTIES. THIS TREND CONTINUES
THROUGH TUESDAY...AS UPPER LOW FINALLY BEGINS TO DRIFT EAST AND
NORTHEAST TO THE MID-ATLANTIC REGION. FORCING FOR PRECIP TODAY
ACROSS OUR SOUTHEAST COUNTIES IS BASED MAINLY IN THE MID-LEVELS...
WITH LITTLE/NO APPRECIABLE INSTABILITY DEPICTED IN MODEL SOUNDINGS.
WARMER SURFACE TEMPS AND VERY SLIGHTLY BETTER MID-LEVEL LAPSE RATES
ON TUESDAY YIELD 200-400 J/KG MLCAPE PER WRF/GFS SOUNDINGS HOWEVER
AND HAVE INCLUDED LOW CHANCE THUNDER POPS TUESDAY AFTN ROUGHLY SOUTH
OF A PNT-VPZ LINE. ACROSS THE REMAINDER OF THE FORECAST AREA... A
PAIR OF PLEASANTLY MILD DAYS ARE ANTICIPATED WITH TEMPS GENERALLY
LOW-MID 70S TODAY AND MORE MID-70S TUES AWAY FROM LAKE MICHIGAN.
NORTHEAST WINDS IN THE 10-15 MPH RANGE WILL KEEP TEMPS CHILLY IN THE
MID-UPPER 50S ALONG THE SHORE FOR THE MOST PART...IMPROVING FARTHER
INLAND.

ON WEDNESDAY...OUR OLD UPPER LOW IS PROGGED TO BE LIFTING ACROSS
VIRGINIA...WHILE WEAK MID-LEVEL SHORT WAVE ENERGY APPROACHES FROM
IA. WITH WEAK MID-LEVEL RIDGE ACROSS OUR REGION WEST OF THE
MID-ATLANTIC CIRCULATION PROGRESS OF THIS FEATURE SHOULD BE FAIRLY
SLOW...MOVING ACROSS NORTHERN IL/NORTHWEST IN WEDNESDAY NIGHT INTO
THURSDAY. FORECAST SOUNDINGS DEPICT INCREASING INSTABILITY WEST OF
THE CWA WEDNESDAY AFTERNOON...WHERE SHOWERS/THUNDERSTORMS WILL
LIKELY DEVELOP AND MOVE INTO NORTHERN IL WEDNESDAY EVENING. THE
COMBINATION RELATIVELY WEAK CAPE...DIURNAL COOLING OF THE BOUNDARY
LAYER AS PRECIP APPROACHES...AND WEAK RIDGING ALOFT ALL SUGGEST THAT
SHOWERS/THUNDERSTORMS WILL LIKELY BE IN A WEAKENING PHASE AS THEY
MOVE IN WEDNESDAY NIGHT. THIS IS SUPPORTED BY MODEL QPF FIELDS WHICH
FOR THE MOST PART DECREASE TO THE EAST ACROSS OUR CWA. HAVE
MAINTAINED FOCUS OF POPS ACROSS THE WESTERN HALF OF THE CWA WED
NIGHT WITH BEST THUNDER POTENTIAL IN THE WEST DURING THE EVENING.
TEMPS AGAIN EXPECTED IN THE MID/UPPER 70S...COOLER LAKESIDE...WITH
DRY CONDITIONS EXPECTED AHEAD OF THIS DISTURBANCE WEDNESDAY.

A TREND TOWARDS COOLER WEATHER BEGINS THURSDAY HOWEVER...AS A COLD
FRONT WHICH TRAILS AN AREA OF LOW PRESSURE MOVING ACROSS CANADA
TUESDAY/WEDNESDAY EVENTUALLY SAGS ACROSS THE AREA THURSDAY AND
THURSDAY NIGHT...AND HIGH PRESSURE BUILDS ACROSS THE NORTHERN GREAT
LAKES REGION. SHOWER/THUNDERSTORM CHANCES ACCOMPANY THE FRONT AS IT
MOVES THROUGH THURSDAY...AND THEN CONTINUE ACROSS OUR SOUTHERN
COUNTIES AS ANOTHER DISTURBANCE AND SURFACE WAVE RIPPLE ALONG THE
FRONT THROUGH FRIDAY. FALLING TEMPS MAY OCCUR ALONG THE LAKE
THURSDAY BEHIND THE FRONT...AND NORTHEAST WINDS INTO FRIDAY WILL
CONTINUE TO COOL THINGS BACK INTO THE MID-UPPER 60S AREA-WIDE
WITH 50S AGAIN ALONG THE LAKE.

SIGNIFICANT AMPLIFICATION OF THE UPPER FLOW IS PROGGED TO TAKE PLACE
ACROSS CENTRAL/EASTERN NORTH AMERICA BEGINNING FRIDAY NIGHT...AS A
STRONG MID-LEVEL SHORT WAVE DIGS TOWARD THE GREAT LAKES REGION. THE
SURFACE LOW ASSOCIATED WITH THIS DIGGING UPPER TROUGH WILL PASS WELL
NORTH OF THE FORECAST AREA EARLY SATURDAY...THOUGH A SHARP COLD
FRONT WILL PLOW INTO THE REGION DURING THE DAY. ALONG WITH A CHANCE
OF SHOWERS WITH THE PASSAGE OF THE COLD FRONT SATURDAY...LONGER
RANGE MODELS ARE IN AGREEMENT IN DROPPING 850 MB TEMPS BELOW ZERO
SATURDAY NIGHT AND SUNDAY...SUGGESTING THAT HIGHS IN THE 60S MAY
FALL IN THE AFTERNOON SATURDAY...AND MAY STRUGGLE TO GET ABOVE 60 IN
SOME AREAS SUNDAY. STRONG HIGH PRESSURE BUILDING SOUTH ACROSS THE
PLAINS AND MIDWEST BEHIND THIS FAIRLY PROGRESSIVE TROUGH SHOULD
ALLOW DRY WEATHER AND PLENTY OF SUNSHINE SUNDAY DESPITE THE BELOW
NORMAL CHILL.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* NORTHEAST WINDS 10 TO 15 KT THIS AFTERNOON...DIMINISHING THIS
  EVENING.


PAW

//DISCUSSION...UPDATED 18Z...

HIGH PRESSURE CENTERED OVER LAKE SUPERIOR DOMINATES NORTHERN
ILLINOIS AND NORTHWEST INDIANA WITH NO SIGNIFICANT WEATHER
EXPECTED. NORTHEAST WINDS BECOMING LIGHT AND VARIABLE
OVERNIGHT...THEN NORTHEAST AGAIN ON TUESDAY.

PAW

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

PAW

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT AND WEDNESDAY...VFR.
THURSDAY...CHANCE OF TSRA. MVFR PSBL IN TSRA.
FRIDAY AND SATURDAY...SLIGHT CHANCE OF SHRA. MVFR PSBL IN SHRA.
SUNDAY...VFR.

KJB

&&

.MARINE...
145 AM CDT

SURFACE HIGH PRESSURE WILL DOMINATE ACROSS THE GREAT LAKES THROUGH
AT LEAST THE FIRST HALF OF THE WEEK. THIS WILL RESULT IN LIGHT WINDS
AND QUIET WEATHER ACROSS LAKE MICHIGAN. HOWEVER...LATER IN THE
WEEK...A COLD FRONT IS EXPECTED TO DROP SOUTHWARD ACROSS THE
LAKE...AND THIS LOOKS TO RESULT IN SOME STRONGER NORTH WINDS UP TO
AROUND 20 TO 25 KT FOR A PERIOD ON THURSDAY AND THURSDAY NIGHT.
FOLLOWING THIS FRONT...A RIDGE OF HIGH PRESSURE IS EXPECTED TO
TEMPORALLY MOVE ACROSS THE LAKE...BEFORE ANOTHER COLD FRONT TAKES
AIM ON THE LAKE NEXT WEEKEND...POSSIBLY RESULTING IN ANOTHER PERIOD
OF STRONGER NORTHERLY WINDS.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$


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